Power Over Ethernet

Effective Cisco IOS XE Release 3.16S, the Cisco ASR-920-12SZ-IM Aggregation Services Router supports Power over Ethernet (PoE). PoE is the ability for any LAN switching infrastructure to provide power over a copper Ethernet cable to an endpoint or powered device.

Prerequisites for PoE

Cisco ASR-920-12SZ-IM
Aggregation Services Router supports multiple variants of power supplies. When
using the AC power supplies, approximately 180 watts is used for PoE
functionality, which can be shared by all eight available copper Ethernet
ports.

PoE is applicable only on
the following ports: Gi0/0/0 to Gi 0/0/7

When using DC power
supplies, PoE is supported only if the input feed to the power-supply is 48
volts.

Restrictions for PoE

Configuring a port as a
static port pre-provisions power for that port. This power is deducted from the
central power pool. It is, therefore, advisable to configure a port as an auto
port.

PoE does not support
interface modules (IMs).

The system allocates 180 W of static power. However, if a component
or device tries to draw power over 180 W, the Cisco ASR-920-12SZ-IM Router
silently reloads.

Information About PoE

The Cisco ASR-920-12SZ-IM Router uses the inline power as well as a
global pool of power to power the modules, fans and other subsystems in the
router. This power is alloted to all the powered devices detected on a
first-come-first-serve basis. However, but if many devices are connected, and a
new device is added to the system, the system may run out of power to allot to
the new device. Over-subscription of power could also result in tripping the
power supplies and bringing down modules or even the entire router. In such
cases, PoE can manage power allocation.

Note

In the Cisco ASR-920-12SZ-IM Router, the dual power supplies
function in redundant power mode.

PoE supports the following two modes of operations:

Automatic—The automatic
mode supports POE, POE+, and UPoE power negotiations up to the maximum power
specified by the these different standards. UPoE is a Cisco proprietary
standard, which can draw up to 60 W of power and supports LLDP negotiations. To
enable UPoE mode, ensure that LLDP is not only enabled globally but also at the
port level.

Four-Pair Forced—This mode
is enabled through the command line interface and can be used for third-party
PoE devices that may need more than 30 Watts of power, but are not expected to
have the Layer-2 power negotiation protocol, such as LLDP.

PoE License

PoE can be enabled only through the PoE license. As the PoE ports are controlled by the Port License, you must enable the PoE Port License as well as the PoE license to use this feature. Once you install the PoE license and enable the feature, the router attempts to detect and classify PoE on those PoE ports that are in ADMIN_UP state and the link state in DOWN state.

Installing the PoE
License

To install or upgrade
a license by using the
licenseinstall command, you must have already received
the license file from the Cisco Product License Registration portal at
http:/​/​www.cisco.com/​go/​license (or you already backed
up the license by using the
licensesave command).

How to Configure the PoE

2. To determine how inline power is applied to the device on the
specified port, use the power inline command:

3. If the interfaces tries to draw more power than negotiated
through LLDP, the
powerinlinepoliceactionerrdisable command sets the port to errdisable
mode.

4. Exit the configuration mode by running:

DETAILED STEPS

Step 1

In the global config mode, select the interface to configure.

Example:

Router(config)# interface gigabitethernet 0/0/1

Step 2

To determine how inline power is applied to the device on the
specified port, use the power inline command:

Example:

Router(config-if)# power inline

Use one of the following options with the above command:

auto—Enables the device discovery
protocol and applies power to the device, if found.

four-pair—Enables the four-pair mode.

never—Disables the device discovery
protocol and stops supplying power to the device.

police—Enables inline power policing;
optional if entering the no form of the command. Default is disabled.

static—High priority PoE interface. The
Cisco ASR-920-12SZ-IM Router preallocates power to the interface, even when
nothing is connected, guaranteeing that there will be power for the interface.
You can specify the maximum wattage that is allowed on the interface using the
powerinlinestaticmaxvaluecommand. If you do not specify a wattage, the switch
preallocates the hardware-supported maximum value of 60 W. If the switch does
not have enough power for the allocation, the command will fail, after which
you must execute the
shut/noshut command to initiate the detection of the
powered device.

max—(Optional) This parameter configures
the maximum power that a powered device can draw.

Step 3

If the interfaces tries to draw more power than negotiated
through LLDP, the
powerinlinepoliceactionerrdisable command sets the port to errdisable
mode.

Example:

Router(config-if)# power inline police action errdisable

Step 4

Exit the configuration mode by running:

Example:

Router(config-if)# end
Router(config)# end
Router#

Verifying the PoE Configuration

The following is a sample
output of the
showpower command:

Router# show power
Power Summary Maximum
(in Watts) Used Available
---------------------- ---- ---------
Inline Power 0.0 180

RFCs

RFC

Title

There are
no new RFCs for this feature.

—

Technical
Assistance

Description

Link

The Cisco
Support and Documentation website provides online resources to download
documentation, software, and tools. Use these resources to install and
configure the software and to troubleshoot and resolve technical issues with
Cisco products and technologies. Access to most tools on the Cisco Support and
Documentation website requires a Cisco.com user ID and password.

Feature Information for Power Over Ethernet

Use Cisco Feature Navigator to find information about platform
support and software image support. Cisco Feature Navigator enables you to
determine which software images support a specific software release, feature
set, or platform. To access Cisco Feature Navigator, go to
http:/​/​www.cisco.com/​go/​cfn. An
account on Cisco.com is not required.

Note

The table below lists only the software release that introduced
support for a given feature in a given software release train. Unless noted
otherwise, subsequent releases of that software release train also support that
feature.

Table 1 Feature Information for Phrase Based on Module Title

Feature Name

Releases

Feature Information

Power Over Ethernet

Cisco IOS-XE Release 3.16.0S

In this release, this feature was introduced on the Cisco
ASR-920-12SZ-IM Aggregation Services Router.